distribute	reads
0-500	333393
500-800	550117
800-1000	276173
1000-1200	229774
1200-1400	193582
1400-1600	160998
1600-1800	135201
1800-2000	113775
2000-2200	96520
2200-2400	83003
2400-2600	72757
2600-2800	64016
2800-3000	56979
>3000	569527
